The Watec Video Camera - Analysis and Discussion

If you act quickly, you might be able to upgrade your 
capabilies for recording lunar Leonids, and later, all occultations.
The Watec 902H camera is highly recommended for recording 
lunar meteor impacts.  Last night, I used it for the first time to 
image the 10% sunlit Moon's dark side, recording 4 reappearances of 
stars.  It was fantastic, with incredible detail visible on the 
Earthlit dark side, and the 9th-mag. stars showing brilliantly, 
using my 8-inch Schmidt-Cass. and f6.3 focal reducing lens.  The 
Watec camera will clearly be able to record lunar impacts about 2 
magnitudes fainter than the PC-23C, and similar gains are obvious 
for lunar and asteroidal occultations as well.  It has almost the 
same performance as my image-intensified system at a fraction of the 
cost; I bought my Watec 902H from Security Products International, 
Pottstown, PA (phone 610-970-5150) for $340 + $6.63 for shipping, 
but lower costs may be available elsewhere - see the end of this 
message, which also has some more information about operating the 
camera.  The Watec 902H camera is made in Japan and widely used by 
observers there.  Contact information is available at but that is for the American division in Las 
Vegas; you can e-mail them at to perhaps ask them 
about dealers selling the camera in other countries (you might also 
check with security camera and telescope dealers in your country). 
With my telescope, it will make it possible to observe grazes of 9th 
and probably even 10th-mag. stars during the crescent phases, giving 
more opportunities to observe these events closer to home.  It is 
also HIGHLY recommended for asteroidal occultations, making it 
possible to videorecord many more of these events than with the PC-
23C.  Visual observations of asteroidal occultations, especially of 
fainter stars, suffer greatly from always larger-than-reported 
reaction times which always complicates the analysis of those 
events; removing the "personal equation" greatly increases the value 
of those observations.  The larger area as well as the sensitivity 
helps considerably in finding the target star.  Visual observations 
of asteroidal occultations are not useless, and are encouraged at 
least to help define the path limits, but video timings are better.

     Also useful, if you have a Schmidt-Cass. telescope, for 
inceasing the area of the Moon imaged, is a focal-reducing lens; 
this also helps for asteroidal occultations (larger field of view) 
and lunar occultation reappearances.  The f6.3 focal reducer is 
available in the range of $125 to $140 or so from many telescope 
dealers.  Probably even better, for a larger field of view to image 
virtually all of the Moon's dark side, is the Meade Series 4000 CCD 
f3.3 focal reducer available for $144.95 from Focus Camera, Inc. in 
Brooklyn, NY (phone orders 888-221-0828), and probably from some 
other Meade dealers.  I just received mine today, and it fits my C-8 
since Meade and Celestron backs are the same.  I hope to try it out 
tonight and will send another message only if I have any problems 
with it.

     As mentioned in my message in early August, the Watec 902H is 
very small (32mm on a side) and operates essentially the same way as 
the common Supercircuits PC-23C (but it has just an RCA output 
rather than BNC video output, so you don't need a BNC-to-RCA 
adaptor) and is powered the same way, with 12V DC, with the same 
power cord available from Radio Shack - see details in the video 
information on the IOTA Web site at
Don't through away your PC-23C since it's handy as a 
microphone/mixer to record sound (WWV); the Watec doesn't have a 

Frank Anet writes, and I concur (and add some more information):
The standard high sensitivity setting on the WAT-902H is useless, as 
the noise background is very high, greatly reducing the dynamic 
range, and the sensitivity is no better than with the low setting. 
The cover on the back of the camera needs to be removed (micro-size 
Phillips screws) to get to the ultra-micro switch to change the 
sensitivity to low (the camera is extremely small and light weight). 
On the low setting, the background noise for a dark scene is still 
greater than necessary (but much reduced from the high setting and 
certainly acceptable).  I permanently set the sensitivity to low.  
When observing lunar occultations, it behaves in the same way as 
does the PC23C, so that the gain is reduced automatically if too 
much of the bright side of the moon is visible (or also if there is 
a lot of glare from the invisible bright limb). Like the PC23C, it 
has a switch to control the exposure time (either 1/60 second or 
automatic).  For dark images, these two settings give the same 
     The sensitivity is adjusted from high to low with a microswitch 
that can be reached only by taking off the back plate of the camera.  
Frank recommends a No. 00 Phillips screwdriver to remove these small 
screws; the screwdriver available in the "Radio Shack" kit works, 
according to one source.  But I was able to remove the screws with a 
No. 0 Phillips screwdriver.  With the back removed, the tiny white 
sensitivity microswitch (not labelled) is mounted on the right side 
of the right side card (looking down into the camera with the RCA 
video output jack up), about a 4th the size of the shutter on/off 
switch on the left side that is accessible through a hole in the 
back plate.  The sensitivity microswitch comes in the up (high 
sensitivity) position; just use a small object, or your fingernail, 
to push it down).  Then reattach the back plate (last night, I 
observed without the back plate on, wanting to know what would 
happen when I changed from high to low sensitivity, but after seeing 
the results, the much higher noise with high sensitivity, I'm going 
to keep it on the low setting).

More about sources for the Watec 902H:

Tony Cook wrote in Aug.:
As for prices - I hunted around on the web. The price
for the 902HS at the following site is claimed to be $350
but when I phoned up and asked they gave me a price of $320?
and the 902H was under $300.  (the 902H is recommended; tests show 
that the 902HS is noisier, but not really more sensitive for 
detecting stars, than the 902H).
[this is the route I followed, but the "under $300" price doesn't 
 seem to be available now.  David]

Frank Anet wrote earlier:
I purchased a Watec video camera (WAT-902H) from Rock House Products 
International, 2 Low Avenue, Suite 205, Middletown, New York 10940, 
because of its "Ultra Low Light" ability and "Incredible Low Light 
Operation", as quoted on the web site.  The price was
about $500, but that was several months ago; it is probably cheaper 
there now.

David Dunham, IOTA, 2001 Nov. 12 

The f3.3 focal reducing lens that I mentioned in my last
message works fine with my C8; I just recorded the reappearance
of 7.0-mag. ZC 1976 at only 5 deg. altitude above the
eastern horizon.  The horizontal width of the field of
view is almost 25', enough to take in most of the Moon's
dark side, and a little more of the area than I could
record with the PC-23C on my C-5 with f6.3 focal reducer
that I used for the 1999 lunar Leonids.

And from down under, Stephen Russell writes about sources
for the Watec 902H camera:

Date: Tue, 13 Nov 2001 10:01:18 +1100
To: Joan and David Dunham 
From: Stephen Russell 
Subject: Re: Worldwide lunar Leonids; fantastic Watec 902H camera

Hi David.

I did a quick web search for the GW-902H camera, and found several
places selling it for less than $300.

$290 at
$290 at
$289 at
$290 at
$254 at

That $254 price looks good.

Good luck with the Leonids.


Good luck with your observations!

David Dunham, IOTA

Watec videocameras, first, message from Tony Cook:
Joan and David Dunham wrote:

Yes, the Watec cameras you mention are more sensitive than the
PC-23C, not by a factor of 200, but they do seem to be more
sensitive by more than 1.0 mag.  I'm copying this to a couple
of observers who have them.  I plan to buy one soon myself.
They don't have a microphone, but you can use your PC-23C for that.

I went for the Watec 902-HS because of the claimed 0.00015Lux
sensitivity, but can confirm that its unlikely to achieve this
sensitivity because you get swamped by noise. Maybe if it was
cooled down to -20C to -30C the thermal electron noise might be
reduced, but I'd rather not try this. The Watec cameras are also
more prone to cosmic ray events, but this is possibly because
they are more sensitive than the PC23Cs. When folks ask me about
the Watec camera I strongly suggest the Watec 902H, its slightly
cheaper and there is no real gain in sensitivity due to the noise
problem. The dip switches for the camera sensitivity are inside
but there is a socket on the outside for electronic control of
gain and expsoure etc. It does not have a microphone, but I feed
the video output into my digital camcorder, and pipe audio from 
a S/W radio along a phono cable into the audio socket of the

Now for some good points about the Watec cameras. Despite
the noise problem, I am pretty happy with what mine can do over
my other PC23C camera. Firstly its got a larger imaging area
1/2" chip (watec) 1/3" chip PC23C so I can pick up more of the Moon
- excellent for looking for lunar impact flashes. Secondly its
a piece of cake to attain 10th mag occultations next to the
Earthlit limb - actuallly any fainter and and you will have
problems seeing the moment of occultation cause the Earthlit
limb mag per pixel is something like this. Thirdly because
of its near IR sensitivity, 11th or 12th mag K and M spectral
type stars show up really strongly. Fourthly the difference between
visibility of Earthlit features is on the PC23C you can sort of see
the main seas, and a few bright craters, but with the Watec 902
camera you get to see a a much clearer picture. BTW I use
a 8" f/5 Newtonian and have used both cameras at Newtonian
focus to minimize glare problems - the PC23C gets me down to
8th mag definitely, the Watec goes clearly down to mag 10, and
fainter in the case of red stars. Its also excellent for getting 
spectra of stars brighter than mag 5 next to the Earthlit limb if
you are into occultation spectroscopy.

As for prices - I hunted around on the web. The price
for the 902HS at the following site is claimed to be $350
but when I phoned up and asked they gave me a price of $320?
and the 902H was under $300.

Hope this helps? Some examples of 1/30sec exposure frames and 
effective 1/10th sec exposures can be found on my FTP site:

Dr Anthony C. Cook,  Center for Earth and Planetary Studies,
National Air and Space Museum, Smithsonian Institution, 
Washington D.C. 20560-0315.  
Fax. (USA) 202 786 2566          Tel. (USA) 202 633 9748
e-mail:  tcook@n...
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 

- and from Frank Anet, fanet@e...


Although I have mentioned to you that my Watec 902H is more sensitive 
than my PC 23C (Topica) camera, I don't think that I had sent you the 
correspondence that I had with a person at Watec in mid 1999. I sent 
Watec an e-mail message and got back a reply (given below), but I did 
not follow up the matter with them. However, it is clear to me after 
this correspondence and some messages by others in the VideoAstro 
List that the sensitivity claimed by Watec is not only useless, but 
also deceptive and perhaps even fraudulent (and they have not changed 
their claims). The Watec 902H does have very good sensitivity, in 
part due to the use of a 1/2 inch CCD sensor instead of the 1/3 inch 
one in the PC23C. This increases the area of the pixels and under 
certain conditions increases sensitivity. The larger detector area 
also gives a wider field of view and this makes observations 
generally more convenient.

Watec have introduced a new and supposedly more sensitive version of 
the camera, the Watec 902HS. I bought one of these a year ago, but 
found that its ability to see weak stars was less than the Watec 902H 
by about 0.5 to 1 magnitude (the tests were done on several occasions 
by repeatedly switching the cameras on the telescope, a process that 
takes less than a minute). The video gain on the Watec 902HS (at High 
Gain, when its high sensitivity is supposed to occur) has been 
boosted to a ridiculous value, so that the dynamic range is very low 
and the background (camera amplifier) noise is extremely high. I use 
the Watex 902H at LOW sensitivity (it has switchable LOW and HIGH 
settings, accessible only by removing the back plate), but even then 
the gain is really too high by a factor of at least 3. This reduces 
the dynamic range, and is only of value if the output is sent to a 
(very cheap) video monitor that has no brightness and contrast 
control. The 902HS does have (difficultly accessible) controls of the 
gain, back light and exposure settings not present in the 902H, but I 
would recommend not getting this model (it now seems to have 
displaced the 902H on the Watec web site). The web site also features 
the Watec LCL-802H "camera board" which claims a "minimum 
illumination" of 0.0003 Lux (in flashing lights, for emphasis). This 
means that the camera can see under these conditions (but what they 
do not say is that this is provided the object, e.g., letters, are 
black and white, and no greys need to be distinguished).

Under normal conditions, the best sensitivity of the Watec, in my 
experience, requires careful focusing and the use of a fairly short 
telescope focal length, preferably less than 100 cm. Just like the 
PC23C, the Watec 902H requires positioning the Moon during an 
occultation time measurement so that not too much light from the 
bright limb reaches the detector, otherwise the automatic gain 
control will reduce the gain drastically and prevent the more or less 
dim star from being visible.
I hope that this is useful. Sorry for the long message!

Frank Anet

At 1:33 PM -0700 4/13/99, Frank Anet wrote:

>To Watec technical Department:
>I purchased a Watec video camera (WAT-902H) from Rock House Products 
>International, 2 Low Avenue, Suite 205, Middletown, New York 10940, 
>because of its "Ultra Low Light" ability and "Incredible Low Light 
>Operation", as quoted on the web site.
>The WAT-902H is advertised (e.g. on both the and on the 
>Watec web site) as having a Minimum Illumination of 0.0003 lux-f1.4 
>lens for AGC set to High and 0.002 lux-f1.4 lens for AGC set to Low. 
>These are amazing specifications since I have not seen any other 
>commercial video camera claiming better than a Minimum Illumination 
>of 0.01 lux with an f1.4 lens.
>However, this "incredible" low light performance is not what I get. 
>I find more like 0.006 lux-f1.4 lens with the AGC set to Low and 
>setting the AGC to high only amplifies both the signal and the 
>noise, so that dimmer object details cannot be resolved than at the 
>Low AGC setting. Thus, the performance is a bit better than the 
>Watec WAT902B camera, which has a 0.01 lux specification. But my 
>camera (serial number 00289) is clearly labeled as a WAT902H.
>I was attracted by the WAT902H specifications because I want to use 
>this camera for amateur astronomy (and I am sure many others would 
>want to do so if the specifications are correct). I have been using 
>a PC-23C camera (Taiwanese-made and labeled Topica on the camera 
>body; a 1/3 inch Sony CCD chip is claimed to be used in this camera) 
>sold by Supercircuits in Texas.  The PC-23C has become very popular 
>with amateur astronomers, and it has a claimed Minimum Illumination 
>of 0.04 lux at f1.8, which corresponds to 0.024 lux f1.4. When I 
>tried the WAT902H with my telescope, just replacing the PC-23C (both 
>have CS lens threads), I got a little better result with the WAT902H 
>than with the PC-23C, but with a much higher background noise for 
>the 902H, and this made the comparison difficult. This test was done 
>with the factory setting of AGC, i.e., set to High.
>After some difficulty, I managed to undo the screws at the back of 
>the 902H (both a big camera and video store and a jeweler were 
>unable to remove the screws) and thus I will not need to send you 
>the camera back (I was given a repair number of 094). I finally 
>found and bought a tiny No 00 Phillips screw driver and it would be 
>nice if tool information, or an actual screw driver --not to mention 
>a tiny Allen wrench for the front lens adjustment-- were provided. 
>Also, why not make a small slot in the rear panel, which does not 
>seal hermetically anything inside, to allow external access to the 
>AGC switch?  Even better, please, please, provide an external 
>continuous adjustment of the gain (is there any way I can modify the 
>camera to do this; I would be very interested even if it voids the 
>warranty, etc.).
>After setting the AGC to Low, the background noise level (no light) 
>was just a little greater than that from the PC-23C.  I then used an 
>Ermitec 12.5 mm CCTV lens with focusing and iris controls (f1.3 to 
>f16) in a darkened room to observe printed matter with each camera, 
>switching back and forth several times. In both cases the image was 
>displayed on a large screen Pioneer color TV set (900 lines 
>resolution) with the brightness control set to maximum. With no 
>camera connected, the screen was black. With either camera connected 
>(no light), the screen had significant, but not overwhelming noise. 
>With each camera, I adjusted the lens iris down so that a given 
>feature of the object was just discernible. I thus found that the 
>WAT902H was just under 2 stops more sensitive than the PC-23C (e.g., 
>with the WAT902H, I could make out features at f11 that required 
>more light with the PC-23C, so that even f8 with the PC-23C was 
>worse and only at f 5.6 was the PC-23C very slightly better than the 
>WAT902H). A two-stop difference is a factor of 4 in light intensity, 
>so, using the PC-23C as a reference, I calculate the light 
>sensitivity of the WAT902H at AGC set either High or Low as 0.006. 
>For this to be 0.002, the PC-23C would need to be three times more 
>sensitive than claimed, or for my testing to in error by a factor of 
>three (I could be off by 50%, but I doubt very much that I could be 
>in error by 300%). Maybe the standard way of measuring Minimum 
>Illumination gives the numbers that are quoted for the 902H camera, 
>but if so these numbers are completely misleading for the users of 
>the cameras, as I see it, and as I am sure most other users would 
>see it.  Clearly, a specification of 0.0003 lux-f1.4 at AGC-Hi is 20 
>times more sensitive than it really is, in my view. The WAT902H does 
>have a fantastic sensitivity of course, but unfortunately, not what 
>is claimed.
>Please indicate if I am wrong. I would appreciate learning how you 
>measure the Minimum Illumination (or a reference to the method you 

At 12:19 PM -0700 4/19/99, Watec America Corp wrote:

>Thank you for your e-mail.
>In security/ Surveillance industry there is no standard
>how to decide minimum illumination while TV industry
>tells minimum   illumination is at point 50% of 100IRE
>i.e. 50IRE is obtained on white section.
>Therefore in this industry manufacturers decided by
>human eye it by using chart.
>When it becomes impossible to identify black and white
>on chart it is minimum illumination. This figure can be
>different between manufacturers.
>We would appreciate learning how you measure the
>minimum illumination.
>Best Regards,
>S. Yamaguchi

     I purchased a Watec 902H camera and received it
last Friday.  Last night, it was clear here, but there
was a full Moon.  The camera performed rather well,
just detecting 10th-mag. stars with an f/6.3 focal
reducing lens on my C-5.  The wider field and greater
sensitivity gives the camera a big advantage over the
less expensive Supercircuits PC-23C for recording and 
finding medium-brightness stars for asteroidal 
occultations.  The camera is considerably smaller than 
the PC-23C, being cubical about an inch on a side.

     However, the camera is quite noisy, considerably 
more than the PC-23C.  Mine also has about half a
dozen hot pixels that look like the faintest stars,
but I can tell them from the stars because they don't
move like the stars, and stars usually illuminate a
few pixels.  I have not tried to open the back of the
camera, as Frank Anet described in his message about
the camera that I distributed to the IOTAoccultation
e-group list on Aug. 5.  I didn't distribute that
message to the AstroAlert list then, so I'll do that
after sending this message.  Frank, you mentioned
finding and buying the small screwdriver needed to
open the back to set to the recommended lower 
sensitivity to reduce the noise.  Were you able to
buy it at an ordinary local hardware store?

     In spite of the noise, I'm happy with the
larger area and approximately 1.5-mag. gain over the
PC-23C, and look forward to using it for dark-limb 
lunar events during the crescent phases.



The (thin aluminum) back plate of the Watec 902H camera is held by 
four very small screws, one at each corner. These steel screws appear 
to be self-threading and apparently were inserted into unthreaded 
holes in the (aluminum) body of the camera during manufacture, as far 
as I can tell. This is an inexpensive method, compared to using 
threaded holes and normal threaded screws and ensures that the screws 
do not fall out because of vibrations.

  BUT, the first time you try to remove these screws may not be very 
easy. A properly sized Philips screw driver (a #00) helps. #2 and #1 
Philips screw drivers are ubiquitous, but the #0 (the next smaller 
size) are much less common, and #00 are rare, but can occasionally be 
found in some local hardware stores (#000 also exist, but I have 
never seen one!). MacMaster-Carr has them. You might try Sears.

Just insist that you want a #00 and nothing else. Doing a web search 
with Google (my favorite search engine, for "Phillips 
#00 screw driver" provides useful information (including a tip from a 
camera-repair tool seller that threaded camera and lens screws are 
sometimes sealed with Loctite, and that trying to remove such screws 
breaks either the screw or the screw driver, unless acetone is 
applied first).

Even with the proper screw driver, one needs to grab the Watec camera 
firmly and apply a fair amount of force to the screw driver as it is 
being turned, so that the screw driver head does not slip and ruin 
the screw head. Once the screw has been removed and put back, 
subsequent removals are much easier. The Low-High gain switch is a 
minute rectangular slide switch and it is fairly stiff and does not 
tend to move because of vibrations. Moving the switch is best done 
with a something like the end of a pair of tweezers. Make sure that 
the slide is fully on one side or the other. In my opinion, the 
camera should never be used with the High gain setting (the factory 
default), as sensitivity is not gained and dynamic range is lost.

Concerning the hot pixels, I also have about a half dozen in my 902H. 
When the camera was new, there were none. Sometime after hot pixels 
gradually appeared, my camera went dead and I returned it to Watec, 
who fixed it free of charge. The returned camera, which may have been 
a replacement camera, had no hot pixels initially, but hot pixels 
gradually returned. The hot pixels are barely visible when viewing a 
scene in normal light, and have never interfered with astronomical 
occultation use, although they are esthetically quite unpleasing.

Frank Anet

Return to the Main Index